1. Field of the Invention
The present invention relates to a method of fabricating a component having an internal tooth profile such as a multiple disc clutch drum or an internal gear and to a rolling machine thereof
2. Description of the Related Art
For example, a large number of methods using a press machine and a die have been reported as means of fabricating a component having internal teeth such as an internal gear or a multiple disc clutch drum including several friction discs. However, since the amount of elastic deformation increases as the size of a press or a die increases, high machining accuracy cannot be expected.
On the other hand, in the field called rolling, there are two main conventional techniques as a method of fabricating a component having an internal tooth profile such as a multiple disc clutch drum or an internal gear.
According to one of the methods, a material to be processed, which has circular inner and outer circumferences, is inserted and fitted into a bar-like inner die having concavity and convexity obtained by transferring and die-sinking an internal tooth profile to be finally obtained so that their inner diameters are aligned. At least one point on the outer circumference of the material is pressed to be deformed in a centripetal direction by a roller, a spatula or the like. The point of application is sequentially moved in a circumferential or axial direction so as to transfer the inner die profile to obtain a component having internal teeth. Leaving aside the question of superiority, this method is characteristic in that the number of teeth of the bar-like inner die and that of the obtained internal teeth are identical with each other.
In the other method, a rolling tool having a tooth die (necessarily with a less number of teeth than that of internal teeth to be obtained), which meshes with an internal tooth profile to be finally obtained in an inscribed manner, is acted on the inner side of a cylindrical material. In the conventional method, a tooth profile substantially already completed in the sense of forming is present inside the cylindrical material to be supplied. At a rolling step, the rolling tool profile is used merely for finishing tooth profile, crowning, and surface roughness finishing. Specifically, the most important requirements for establishment of this conventional method are that a macro load is low because a tool tip does not come into contact with the material to be processed so that deformation is slight, and the stiffness of the material to be processed prevents roundness from being changed (degraded). As a result, a gripping mechanism having a relatively low stiffness can be used. The presence of the gripping mechanism brings about the unexpected effect of serving for initial rotational phasing between an existing tooth profile and a tooth space of a rolling tool.
[Non-Patent Article 1] Catalogue of a Finishing Gear Rolling Machine for Taper Flank of Internal Involute Spline “GR-151N” fabricated by Yutaka Seimitsu Kogyo Ltd.